Blasting.



T. JOHNSON. BLASTING.

APPLIOATION FILED 110 1.25, 1911.

Patented Nov. 11', 1913.

THOMAS JoHNsoN, or DUDLEY, ENGLAND.

BEASTING'.

Specification of Letters Patent.

Application flled lwovember 25, 1911. Serial N 0. 662,485.

Patented Nov. 11, 19,13.

To all whom it may concern: I

Be it known that I, THOMAS JoHNsoN, a

' subject of the Kingdom of Great Britain, re.-

siding at 7 Hill street, Kates Hill, Dudley, in. the county of Worcester, England, explosives expert, have invented certain new and useful Improvements in or Relating to Blasting, offwhich the following is a specification.

This invention relates to the process of blasting as carried on for instance in mines and it comprises a modeof and means for tamping or stemming the blasting hole after the explosive has been introduced.

The materials previously used or proposed as tamping media have been ineflicient or inconvenient to use, and previously proposed tamping plugs have not been of a character enabling them to efiiciently prevent blowing out. To obviate this latter danger it has been proposed to use in ad- I whitestone dirt or toccy.

dition various chemical compounds. 7

According to my present invention I provide the tamping or stemming in the form of a-dry or comparatively hard plug but which plug has further'the characterictic that when damped or immersed in water it becomes soft or plastic and afterward readily sets and binds with the adjacent coal or material so providing a stemming of resisting qualities substantially equal to those of the material to be blasted, and preventing blowing out.

A suitable and cheap tamping material for. the purpose of the present invention is argillaceous shale commonly known as The argillaceous shale as found in nature is ground, treated with water, and in its plastic state formed into rods' or circular lengths as for instance by being pressed through a perforated plate. The object of grinding or pulverizing the, shale is to eliminate or reduce to a powder any grit present which might otherwise damage the detonator wires in the process of tamping. While: in the,

plastic state the rods or lengths of treated shale are cut or divided into short cylinders and allowed to set or harden ready for use, in which form the material is' portable, particularly convenient and quick to mampulate.\ It is further found that, the grinding operation enables the plugs to be better formed since the finely ground material possesses a remarkable degree of cohesion.

In order to facilitate the dampin To facilitate an understanding of the'invention reference is directed to the apthroughout of the primer plugthat is to say that part of the stemming which is placed next to the explosive, it is provided with a number of holes, grooves," passages or the like extending preferably throughout its length. The plug introduced after plug may if desired the first or primer be solid and undamped.

By reason of-the smooth surface which is obtainable with plugs'made as aforesaid the possibility of the-plugs taking coal dust with them in the process of stemming is almost entirely removed, whilethe detonator wires or fuse may without of damage be accommodated in one or more grooves in the plug. Such a groove may commence at the side of the plug and incline to the center of the end nearest the charge, thereby avoiding as faras possible thefnecessityfor the bending of the wires use.

pended sheet of drawings, on which-' Figure 1 is a diagrammatic representation illustrating the holding-and stemming of a.

blasting operation and in which a plug in accordance with the present invention is 'in use. primer part of a plug. Fig. 3 illustrates in perspective one of the solid parts of theplug introduced after inserting theprimer Fig. 2 illustrates in perspective the,

In the drawings a represents the powder or charge, b the primer plug advantageously having the longitudinal perforations b forthe purpose aforesaid of fgcilitating damping, a the preferably. solid plugs introduced after theprimer plug has been inserted, d a detonator wire. l

I have found in practice that argillaoeous shale readily softens when wet or moistened and that it subsequently sets hard. Furthermore, after it has been wet. to soften the same, and after subsequently hardening, it will readily soften 'when again dampened or wetted, and will not only sethard, but will coalesce with the coal,'stone or other material in which the blast openingiis formed. This property of the material greatly enhances its value when used in ac"' cordance with my invention since it permits of the plugs being completely formed in shape ready for use and this feature greatly facilitates transport and saves loss, and it also facilitates handling by the operator in plugging the blast opening;

In tamping, after the explosive a has been placed in position, one of the primer plugs b,

as shown in Fig. 2, is inserted after being dampened. then the primer plug 6 is immersed in water in the opening admit water to the interior so that the softening process is greatly facilitated substantially throughout 'the cross-section oi the plug.

After insertion of the primer plug, any suitable number of solid plugs may be inserted and the plugs are then subjected to a tamping or pressure action thereby closelyconfining the powder. Furthermore the dampened primer plug 0 is reduced in length by reason of this compression or tamping, and is spread outwardly against the wall of the blast opening into a solid mass, thereby closing all of the openings in the primer plug. Because of the plasticity of the plug,

the powder-is 'compressed and therefore the" The plugs c which may or may not be made of material of which the plugs b are made, will then be forced into the opening as illustrated in Fig. 1. If desired the plugs 0 may be made of argillaceous shale and may be dampened before being inserted.

What I claim as my invention and desire to secure by Letters Patent is:--

1. In a tamping or stemming plug composed of argillaceous shale, forming the primer plug with longitudinal passages substantially as and for the purpose specified.

2. A stemming or tamping plug for blasting openings formed of a solid shaped mass of homogeneous material adapted to soften when wet, and to subsequently set hard, said plug being provided with openings, substantially as and for the purpose set forth.

3. A tampmg plug formed by grlndlng argillaceous shale, molding the same, and.

drying the molded plug.

. In Witness whereof I have hereunto set my hand in the presence of two witnesse THOMAS. JOHNSON.

lVitnesses G. B. BRUoKsI-mw, R. L. GooLD. 

